<link rel="stylesheet" href="basics.css">
<style>
.inner {
  border: 2px solid black;
  width: 35px;
  height: 35px;
  display: flex;
  justify-content: center;
  align-items: center;
}
</style>
<script src="../../dist/DragSelect.js"></script>
<button type="button" class="item one">
  <div class="inner">1</div>
</button>
<button type="button" class="item two">2</button>
<button type="button" class="item three">3</button>
<script>
    const ds = new DragSelect({
        selectables: document.querySelectorAll('.item'),
    });
</script>
